Pruning and Oak Wilt

Well, it’s that time of year again, when most arborists are inundated with the question “Is it safe to prune my oaks now?” or, “Why are there signs in my neighborhood saying I shouldn’t prune my oaks now?” These signs are particularly prevalent in northwest Austin.

live oak leaf symptomatic of oak wilt

For more details about oak wilt, see my dedicated oak wilt page, or go to my previous post on it. But since it is that time of year, I thought I’d revisit the issue here.

Regarding those signs, you’ll notice most of them say “Do NOT Prune Oaks…”, etc. Well, the guidelines they were derived from never said “do not prune…”. They recommended avoiding oak pruning in the spring. The latest version of those guidelines (on my oak wilt page) indicate what oak pruning can (and actually should) be done year-round.

The reasoning behind this is quite logical. First, the oak wilt fungus cannot enter a tree through dead tissue. It must be alive, with open, moist vasculature. This is why experts advise people that painting old wounds is of no use and why wound paint is only of value when it is applied immediately (not hours after the wound is made). It is also why the guidelines state that dead branches can be removed at any time of year. (However, one must be careful about possibly exposing some live tissue when doing this.)

Second, since the disease can enter an oak through fresh wounds, it stands to reason that any such wounds should be eliminated immediately. Limbs rubbing on buildings, or damaged by trucks, or even rubbing against other limbs all cause open wounds. Leaving them until July just doesn’t make sense. By eliminating the damaged or at-risk limbs (using proper techniques and painting the cuts, of course) we eliminate the risk, at least in that spot. Remember that storms, insects and animals (yeah, I’m talking ’bout you, squirrels) cause countless wounds that cannot be prevented.

So back to the signs. What happened was there was a large amount of truly horrific tree pruning in northwest Austin at the time (still is, actually, as is true city-wide), and this led neighborhood leaders to begin a campaign for a seasonal ban on oak pruning altogether (rather than, duh, begin a campaign of educating people about hiring hacks, which would have protected their neighborhood year-round). They even pushed for an ordinance at city hall. Fortunately, several local arborists also met with council members and educated them about the real problem (you’re welcome!). Unfortunately, council chose not to take any action to protect consumers against scammers masquerading as tree companies.

As always, your best defense against dead trees is to only use competent arborists on your property. Keep in mind that this does not simply mean hiring “certified” arborists. Please see my page on hiring an arborist for details.